Thank you everyone.
I live in Yangon, Myanmar and the weather is pretty hot here.
I have changed the trans fluid and even cleaned the fluid particle filter which is inside
the transmission case.
again the problem is still not solved.
In our country, the reconditioned Japan used cars are mostly used and
brand new are rarely seen due to taxes and government's restrictions.
I also have another vehicle named Toyota Belta(japanese domestic) known as Toyota Vios in other countries which is also equipped with CVT.
Unlike my Insight, the Belta operates very smoothly. Not even a little shudder under every driving conditions.